certain states do have the requirement that you finish your internship BEFORE sitting for Step 3. HOWEVER, just get another state to sponsor you. See, you can get ANY State to sponsor you for Step 3, as long as you have graduated from Med school. Many states have no time requirement once you have graduated.
So to summarize, get a different state to sponsor you, then take Step 3 at ANY prometric testing center, regardless of what state sponsored you.
It will not make a difference for your licensure. It's an antiquated system with many relics of regulations. Just take the stupid test during your internship, it will only get harder as you progress through your anesthesia training.